Using directlabels with ggplot2 to label a second layer with data different from the primary layer

Question

I'm using `ggplot2` to make contour plots. I'm trying to make a contour plot with split data because I have data from different time periods for different regions of the plot. I'd like to show them on the same plot, but not have the contours line up. I can produce the contours I want simply enough; here's a similar example: ``` library(ggplot2) library(directlabels) data(volcano) volcano3d <- melt(volcano) names(volcano3d) <- c("x", "y", "z") #Splitting the data into 2 halves volcano3d_1<-volcano3d[volcano3d$x<50,] volcano3d_2<-volcano3d[volcano3d$x>=50,] #Changing the z values of the 2nd half volcano3d_2$z<-volcano3d_2$z+30 #Plotting v <- ggplot(volcano3d_1,aes(x, y, z = z))+ stat_contour(aes(colour = ..level..))+ stat_contour(data=volcano3d_2,aes(x,y,z=z,colour=..level..)) direct.label(v) ``` However, I can't get `direct.label` to add labels to the second part of the map. It seems like the difficulty is with getting it to label a layer that has data different from the primary `ggplo…

Accepted Answer

Use `geom_dl` to label additional layers:

```
WithLegend <- ggplot(volcano3d_1,aes(x, y, z=z, colour=..level..))+
  stat_contour()+
  stat_contour(data=volcano3d_2)
## direct.label labels the first colored layer.
SomeLabels <- direct.label(v)
## Additional labels can be added using geom_dl layers.
MoreLabels <- SomeLabels+
  geom_dl(aes(label=..level.., colour=..level..),
          data=volcano3d_2, method="top.pieces", stat="contour")
```

Using directlabels with ggplot2 to label a second layer with data different from the primary layer

Solution

Problem